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  Subjects -> ENGINEERING (Total: 2167 journals)
    - CHEMICAL ENGINEERING (184 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (94 journals)
    - ENGINEERING (1173 journals)
    - ENGINEERING MECHANICS AND MATERIALS (355 journals)
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    - INDUSTRIAL ENGINEERING (57 journals)
    - MECHANICAL ENGINEERING (81 journals)

CHEMICAL ENGINEERING (184 journals)                  1 2     

AATCC Journal of Research     Full-text available via subscription   (Followers: 3)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 4)
Acta Polymerica     Hybrid Journal   (Followers: 6)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 5)
Advanced Chemical Engineering Research     Open Access   (Followers: 9)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Partially Free   (Followers: 3)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 17)
Advances in Chemical Engineering and Science     Open Access   (Followers: 24)
Advances in Polymer Technology     Hybrid Journal   (Followers: 11)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 5)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 9)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 10)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 4)
Applied Petrochemical Research     Open Access   (Followers: 3)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 6)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 9)
Biofuel Research Journal     Open Access   (Followers: 2)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 6)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Carbohydrate Polymers     Hybrid Journal   (Followers: 9)
Catalysts     Open Access   (Followers: 8)
Chemical and Engineering News     Free   (Followers: 7)
Chemical and Materials Engineering     Open Access   (Followers: 1)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 11)
Chemical and Process Engineering     Open Access   (Followers: 4)
Chemical and Process Engineering Research     Open Access   (Followers: 6)
Chemical Communications     Full-text available via subscription   (Followers: 33)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 25)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 10)
Chemical Engineering and Science     Open Access   (Followers: 3)
Chemical Engineering Communications     Hybrid Journal   (Followers: 10)
Chemical Engineering Journal     Hybrid Journal   (Followers: 23)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 19)
Chemical Engineering Research Bulletin     Open Access   (Followers: 1)
Chemical Engineering Science     Hybrid Journal   (Followers: 17)
Chemical Geology     Hybrid Journal   (Followers: 10)
Chemical Papers     Hybrid Journal   (Followers: 3)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 3)
Chemical Reviews     Full-text available via subscription   (Followers: 156)
Chemical Society Reviews     Full-text available via subscription   (Followers: 34)
Chemical Technology     Open Access   (Followers: 5)
ChemInform     Hybrid Journal   (Followers: 3)
Chemistry & Industry     Hybrid Journal   (Followers: 2)
Chemistry Central Journal     Open Access   (Followers: 5)
Chemistry of Materials     Full-text available via subscription   (Followers: 138)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 6)
ChemSusChem     Hybrid Journal   (Followers: 8)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 3)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal  
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 8)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 2)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 8)
CORROSION     Full-text available via subscription   (Followers: 3)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 22)
Corrosion Reviews     Hybrid Journal   (Followers: 4)
Crystal Research and Technology     Hybrid Journal   (Followers: 2)
Current Opinion in Chemical Engineering     Open Access   (Followers: 3)
Education for Chemical Engineers     Hybrid Journal   (Followers: 4)
Ekologia : The Journal of Institute of Landscape Ecology of Slovak Academy of Sciences     Open Access  
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription  
European Polymer Journal     Hybrid Journal   (Followers: 43)
Fibers and Polymers     Full-text available via subscription   (Followers: 3)
Fluorescent Materials     Open Access  
Focusing on Modern Food Industry     Open Access   (Followers: 3)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 1)
Gels     Open Access  
Geochemistry International     Hybrid Journal  
Handbook of Powder Technology     Full-text available via subscription   (Followers: 3)
Heat Exchangers     Open Access   (Followers: 1)
High Performance Polymers     Hybrid Journal  
Indian Chemical Engineer     Hybrid Journal   (Followers: 3)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 11)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 9)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 20)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 4)
Info Chimie Magazine     Full-text available via subscription   (Followers: 2)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 1)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 4)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access  
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 3)
International Journal of Science and Engineering     Open Access   (Followers: 7)
International Journal of Waste Resources     Open Access   (Followers: 5)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 3)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 5)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 11)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 126)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 8)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 11)

        1 2     

Journal Cover   Chemical Engineering Science
  [SJR: 1.178]   [H-I: 114]   [17 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [2800 journals]
  • 12-Molybdophosphoric acid supported on titania: A highly active and
           selective heterogeneous catalyst for the transesterification of dimethyl
           carbonate and phenol
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): Songlin Wang, Rongzhi Tang, Yuanzhuo Zhang, Tong Chen, Gongying Wang
      12-Molybdophosphoric acid supported on titania (HPMo/TiO2) was prepared by one-step in situ method and first used to catalyze the transesterification of dimethyl carbonate and phenol to diphenyl carbonate, which exhibited excellent catalytic activity. The highly dispersed HPMo and stable Keggin structure played a significant role for the excellent catalytic performance of HPMo/TiO2. With the conditions of weight ratio of HPMo to TiO2 of 1:1, calcined temperature of 300°C, catalyst amount of 0.6g and reaction time 10h, the phenol conversion and transesterification selectivity reached 50.4% and 99.4%, respectively. Moreover, after four consecutive runs, the phenol conversion slowly decreased from 44.7% to 29.5%, and the transesterification selectivity maintained at 99%. The characterization of XPS and FT-IR presented that the transformation of Mo6+ to Mo5+ and the adsorption of reaction intermediate were the key factors for the decrease of catalytic activity.


      PubDate: 2015-08-30T19:50:09Z
       
  • Operation and dynamic modeling of a novel integrated
           anaerobic–aerobic–anoxic reactor for sewage treatment
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): R. Plascencia-Jatomea, I. González, J. Gómez, O. Monroy
      Integrated reactors (IR) combining anaerobic, aerobic and nitrogen removal processes are a viable alternative to reduce operational costs and footprint compared to conventional wastewater treatment plants. An integrated bench scale (6.4L) anaerobic–aerobic–anoxic column reactor (ICR) is developed to remove carbon and nitrogen compounds from sewage of our university campus. The ICR is comprised of an up-flow anaerobic sludge blanket reactor (UASB), a membrane aerated biofilm reactor (MABR) and a denitrifying biofilm reactor (DNB). The global COD removal efficiency (ηC-Global) is ~82% at hydraulic retention time (HRT) of 8.4h. The partial nitrification (PN) process is obtained with an ammonia/nitrite ratio (R a/n ) of 4. The experimental data were used to calibrate and validate an integrated carbon-nitrogen removal model (ICNRM), in order to determine operating conditions for the improvement of the ICR performance, considering the hydrodynamic profile and reaction kinetics. A good agreement between the measured and modeled results is obtained with a least square error function (S) lower than 0.09. The model predicts that the COD removal efficiency at the MABR (ηC-MABR) and nitrite accumulation at the DNB are influenced by the volumetric oxygen transfer coefficient (k L a) and oxygen concentration, respectively. The optimal operation zone for ηC-MABR>90% and R a/n of 1.32 were reached for k L a between 1.26 and 1.36 1/h, and an inlet DO concentration of 1.5 to 1.6mg/L respectively, standing out the importance of calibrating hydrodynamic behavior and kinetics.
      Graphical abstract image

      PubDate: 2015-08-25T21:14:23Z
       
  • Numerical and experimental investigation of induced flow and
           droplet–droplet interactions in a liquid spray
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): Sandip Pawar, Johan Padding, Niels Deen, Alfred Jongsma, Fredrik Innings, J.A.M. (Hans) Kuipers
      An Euler–Lagrange model is presented that describes the dynamics of liquid droplets emerging from a high-pressure spray nozzle in a relatively large volume (of the order of almost a cubic meter). In the model, the gas phase is treated as continuum, solved on an Eulerian grid, and the liquid phase is treated as a dispersed phase, solved in a Lagrangian fashion, with interphase coupling through state-of-the-art drag relations obtained from direct numerical simulations. The droplets are introduced into the system at high velocities, leading to a turbulent self-induced gas flow which is solved using large eddy simulation. Despite the relatively low liquid volume fraction in the spray, the number density of droplets at the nozzle is still more than 1010 m−3, which is why we employ a highly efficient stochastic Direct Simulation Monte Carlo approach to track collisions between droplets. The droplet collision frequency is calculated on the basis of local droplet number density, droplet size and relative velocities of neighbouring droplets within a dynamically adapting searching scope, as described in Pawar et al. (2014. Chem. Eng. Sci. 105, 132–142). We use known correlations from literature to determine the outcome of a binary droplet collision, which depending on characteristic dimensionless numbers can be coalescence, bouncing or, for high velocity impacts, stretching or reflexive separation leading to formation of satellite droplets. Our simulation model is compared with droplet velocities and size distributions obtained from phase Doppler interferometry experiments on an industrial scale hollow-cone pressure swirl nozzle spray. We find semi-quantitative agreement for spray characteristics such as the axial and radial spray velocity, spray jet width, and the dependence of the droplet size distribution on position within the spray. The simulation model enables us to study the relative importance of different droplet collision events occurring in the spray volume.
      Graphical abstract image

      PubDate: 2015-08-25T21:14:23Z
       
  • Measurement and kinetic modeling on photoluminescence stability from
           
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): Susumu Inasawa, Yukio Yamaguchi
      The stability of photoluminescence (PL) intensity from chemically etched silicon microparticles is studied. Etched microparticles have many narrow and deep trenches on surface. They show visible orange–red PL, which decreases in intensity during continuous excitation by ultraviolet light. The intensity of PL partially recovers when the surrounding gas is changed from air to nitrogen. Thus PL quenching consists of both reversible and irreversible processes and we propose a kinetic model that consists of two quenching paths. Adsorption and desorption of oxygen followed by irreversible oxidation of emission sites are considered in the fast quenching pathway, while the slow pathway involves transport of oxygen molecules to emission sites in trenches with poor access. Our model agrees well with experimental data and rate constants of involved processes are determined, with which we discuss kinetics in PL quenching. Possible strategy to increase PL stability is also discussed.
      Graphical abstract image

      PubDate: 2015-08-25T21:14:23Z
       
  • Thermodynamic and kinetic study of the dehydration process of CaO/Ca(OH)2
           thermochemical heat storage system with Li doping
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): J. Yan, C.Y. Zhao
      Thermochemical heat storage material is very promising to realize long-term heat storage. In this paper, Li-doped Ca(OH)2 prepared by ball grinding is compared with pure Ca(OH)2 to study the influence of Li doping amount on heat storage speed by thermogravimetric (TG) experiment. Furthermore, the heat storage capacity (including the reaction enthalpy and specific heat capacity) with Li doping is studied, and the related kinetic control equation is derived. The results show that the heat storage capacity remains almost unchanged with Li doping, but the kinetic process of Ca(OH)2 heat storage with Li doping is divided into two stages which can be analyzed from the molecular structure. There is an interesting coincidence in the reduction of energy between the apparent activation energy and the energy barrier of Ca(OH)2 dehydration process with Li doping. Finally, the theoretical results using the kinetic control equations agree well with the experimental results.


      PubDate: 2015-08-25T21:14:23Z
       
  • The influence and optimisation of electrical parameters for enhanced
           coalescence under pulsed DC electric field in a cylindrical electrostatic
           coalescer
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): Donghai Yang, Minghai Xu, Limin He, Xiaoming Luo, Yuling Lü, Haipeng Yan, Chengkun Tian
      A pulsed DC electric field is usually used to enhance drop–drop and drop–interface coalescence in a water-in-oil (W/O) emulsion. The effect and optimisation of electrical parameters are important when designing an electrostatic coalescer. In this work, experiments were performed with a small-scale electrostatic coalescer and image processing technology using water in crude oil emulsions to investigate the influence of electric field intensity, frequency, duty ratio and rise time. The comparison between experimental data and predicted data based on the two-layer capacitor model of a cylindrical electro-coalescer was also obtained to validate whether the two-layer capacitor model is applicable for a concentric cylindrical electrostatic coalescer. Optimum electric field strength exists for different water content emulsions (525.6kVm−1 for water content of 10% and 338.1kVm−1 for 30%), which suggests that it is higher for lower water content emulsion. There are two optimum frequencies in the low and high frequency ranges. For water content of 10%, the optimum frequency is approximately 20Hz, while for 30%, it is 10Hz in the low frequency range. The coalescence effect is also high when the frequency is 2000Hz. The droplet diameter is largest when the duty ratio is 50% for different electric field strengths, frequencies and water contents. The effect of rise time for pulsed DC is negative and the longer the rise time is, the worse the electrostatic coalescence effect is. The optimum frequency and duty ratio are obtained by using a theoretical formula and an empirical formula. The optimum frequency is nearly the same for the low frequency range especially for emulsions with a water content of 10%, but coalescence effects will increase at high frequency, which is different from the theoretical predicted value, indicating that the theory is applicable in the low frequency range for the concentric cylindrical coalescer. The predicted duty ratio is close to 0.5 and is nearly the same as the experimental results. In the electrostatic coalescer, the waveform of pulsed DC will be distorted to a triangle wave at high frequency. The high-frequency pulsed DC electric field is therefore not suitable for use in an electrostatic coalescer with an insulated electrode.
      Graphical abstract image

      PubDate: 2015-08-25T21:14:23Z
       
  • Two-phase modelling and simulation of the hydrothermal fractionation of
           holm oak in a packed bed reactor with hot pressurized water
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): A. Cabeza, F. Sobrón, F.M. Yedro, J. García-Serna
      Hydrothermal fractionation has been thoroughly studied in order to develop a sustainable process to recover the sugars and/or the biopolymers contained in biomass. However, a physico-chemical model which considers the main involved physical phenomena, like porosity variations, has not been fully developed yet. Thus, the objective of this work was to approach a more realistic model than other yet published, incorporating also a novel reaction pathway for biomass fractionation. It establishes that cellulose and hemicellulose begin their fractionation in the solid, breaking in water-soluble oligomers and sugar. Besides, deacetylation reactions and insoluble oligomer formation from cellulose were considered. Kinetics followed the Arrhenius׳ law and and it has been demonstrated that an autocatalytic kinetic model can be successfully used to simulate the biomass breaking in soluble oligomers. The process was carried out in a tubular reactor charged with 5g of holm oak and continuously fed with hot pressurized water. To assess the mass transfer between the solid and liquid, 4 volumetric flows (5mL/min, 10mL/min, 20mL/min and 40mL/min) and two particle diameters (3mm and 6mm) were used. In the same way, temperature was set between 175°C and 207°C. The latter was the main variable due to its effect in biomass solubility and kinetics. The model was solved by the Runge-Kutta׳s method with 8th order of convergence and its discretization was performed by a new modification of the orthogonal collocation method on finite elements. It was validated by fitting total organic carbon (TOC) with Absolute Average Deviation (A.A.D. between 16.3% and 55.8%), acetic acid concentration (A.A.D. between 44.4% and 84.4%) and pH profiles (A.A.D. between 5.6% and 9.7%). Besides, the mass transfer between the solid and the liquid was checked and the deviations of the simulation were lower than 8.5%.
      Graphical abstract image

      PubDate: 2015-08-25T21:14:23Z
       
  • Emulsion terpolymerization of St/MMA/BuA: Modeling of composition, number
           of particles and the influence of n-DDM on the molecular weights
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): Javier Alejandro Díaz-Ponce, Humberto Vázquez-Torres, Carlos Martínez-Vera
      The influence of n-dodecyl mercaptan (n-DDM) on the molecular weights distribution of the styrene/methyl methacrylate/butyl acrylate (St/MMA/BuA) terpolymer was studied. First, a kinetics emulsion terpolymerization model based on Nomura’s model for copolymerization was developed. The predicted data by this model was compared with those obtained for batch, semicontinuous polymerization, as well as seeded experiments for the St/MMA/BuA system. A composition near to the unitary azeotrope of methyl methacrylate (MMA) was calculated and used to estimate the M w of a terpolymer uniform in composition synthesized by a seeded process. It was established that a higher proportion of BuA makes the model of weight fraction of polymer W p in the particle more suitable for simulating the gel effect on the propagation rate coefficient k p . Likewise, this model of gel effect upon k p is significant for both the semicontinuous processes with lower monomer addition rate and the seeded process.
      Graphical abstract image

      PubDate: 2015-08-25T21:14:23Z
       
  • Laboratory and pilot plant fixed-bed reactors for Fischer–Tropsch
           synthesis: Mathematical modeling and experimental investigation
    • Abstract: Publication date: 22 December 2015
      Source:Chemical Engineering Science, Volume 138
      Author(s): Vadim S. Ermolaev, Kirill O. Gryaznov, Eduard B. Mitberg, Vladimir Z. Mordkovich, Valentin F. Tretyakov
      The present work describes the development of a comprehensive two-dimensional heterogeneous model of a fixed-bed reactor for Fischer–Tropsch synthesis. The chemical kinetics for cobalt-based catalysts is modeled on the basis of the LHHW approach. The intraparticle transport model takes into account the fact that the catalyst pores are filled with liquid hydrocarbons and water due to capillary condensation under realistic conditions. The validity of the reactor model is tested against the experimental data from laboratory and pilot plant fixed-bed reactors over a wide range of operating conditions. Detailed numerical simulations are performed to investigate the effect of major process parameters on the reactor performance.


      PubDate: 2015-08-25T21:14:23Z
       
  • Effect of chemical structure of organics on pore wetting
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Xingxun Li, Hui Fan, Xianfeng Fan
      Pore wetting is significant for understanding fluid behaviour in porous media. In this paper, a range of organics with similar surface tensions were used to investigate the effect of chemical structure on glass pore wetting. We measured contact angles of organics in a single glass capillary. Our results indicate that the chemical structure of organics does significantly affect the contact angle in a single glass pore. The amphiphiles have similar surface tensions, but their contact angles vary greatly with their chemical structures. The amphiphiles with functional groups have larger contact angles than the non-polar organics, and in the order of θ – OH > θ – NH 2 ≈ θ – COOH . The contact angle of amphiphile in a glass pore increases with the straight alkyl chain length. The straight alkyl chain contributes to the pore contact angle most and the side chain on the carbon of backbone tends to reduce the pore contact angle. The symmetrical molecular structure gives the smallest contribution on the pore wetting. In addition, the contact angles of amphiphiles were also measured in a hydrophobic PMMA (poly(methyl methacrylate)) pore, and compared with those in a hydrophilic glass pore. The results indicate that the chemical structure has no contribution on hydrophobic pore wetting.
      Graphical abstract image

      PubDate: 2015-07-28T04:26:58Z
       
  • A new approach for determination of single component gas hydrate formation
           kinetics in the absence or presence of kinetic promoters
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Bahman ZareNezhad, Mona Mottahedin, Farshad Varaminian
      The kinetics of single component gas hydrate formation processes at isochoric or isobaric operating conditions with and without using the kinetic additive have been experimentally and theoretically determined. In the proposed kinetic model, the coupled equations of hydrate stability and mass balance are solved such that the conventional equilibrium calculations for expressing the driving force is not necessary. The driving force, occupancy factor, Langmuir constant and free energy change are expressed in terms of gas hydrate former composition in the liquid phase. The introduced kinetic rate constant which is the only adjustable parameter of the proposed model is a weak function of the temperature and a strong function of the surfactant concentration. It is shown that the determined kinetic rate constant is independent of the employed isochoric or isobaric operating modes and is independent of the operating pressure. The overall AAD% and R 2-value of the calculated gas molar consumptions regarding methane (C1), ethane (C2) and carbon dioxide (CO2) hydrate formation processes at isochoric or isobaric operating conditions with and without using the sodium dodecyl sulfate (SDS) kinetic promoter are about 1.91% and 0.997 respectively suggesting the excellent accuracy of the proposed kinetic model.


      PubDate: 2015-07-24T04:13:18Z
       
  • New methods for flow regime identification in bubble columns and fluidized
           beds
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Stoyan Nedeltchev
      New methods for flow regime identification were developed and applied to photon count time series measured in a bubble column (0.162m in ID) and fluidized bed (0.438m in ID). The signals in the bubble column (operated with an air-therminol system) were measured by means of Computed Tomography (CT), whereas the data in the fluidized bed (operated with an air-polyethylene system) were recorded by means of Nuclear Gauge Densitometry (NGD). The hidden information in the time series was extracted by means of two new parameters: entropy (bit/s) and information entropy (bit). Both of them were calculated on the basis of multiple reconstructions of the time series. In the case of the bubble column, the well-pronounced local minima were used for identification of three transition velocities (0.04, 0.08 and 0.13m/s). They distinguished the boundaries of the bubbly flow, transition and churn-turbulent flow regimes. In the case of the fluidized bed, the minimum fluidization velocity (0.086m/s) and minimum bubbling velocity (0.12m/s) were also identified on the basis of the well-pronounced local minima in the profiles of the new parameters. They distinguished the boundaries of both the transition and bubbling fluidization regimes.


      PubDate: 2015-07-24T04:13:18Z
       
  • Model-based cost optimization of a reaction–separation integrated
           process for the enzymatic production of the rare sugar d-psicose at
           elevated temperatures
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): N. Wagner, A. Bosshart, S. Wahler, J. Failmezger, S. Panke, M. Bechtold
      The integration of biocatalysis with continuous separation of product and substrate constitutes an attractive option for overcoming the intrinsic yield limitation in enzymatic reactions that suffer from an unfavourable position of the equilibrium. One example is the recently established continuous process combining enzymatic epimerization in an enzyme membrane reactor (EMR), simulated moving bed (SMB) chromatography and nanofiltration for the high-yield production of the rare sugar d-psicose from its bulk epimer d-fructose with recycling of the unused epimer to the EMR. In this work, we present a first, comprehensive analysis of this novel reaction-separation process concept on the basis of an integrated process model. Therefore, a process model consisting of a continuous stirred tank reactor model with reversible Michaelis–Menten kinetics for representation of EMR operation, a transport-dispersive true moving bed model for representation of SMB operation and an ideal filtration model was constructed. As enzyme costs are particularly difficult to estimate due to their strong dependence on the reactor temperature, we further established a model-based procedure for characterizing the biocatalyst in terms of operational stability and activation as a function of the reactor operating temperature. The integrated process model then enabled the identification of optimum operating points for a fully integrated process operation. First, the established design procedure was used to implement a highly productive run on our existing lab-scale plant (i.e. 2.3kg of d-psicose per L of SMB column volume and day and 4.5kg d-psicose per g enzyme and day), where Dpsicose was produced both at high purity (≈ 98%) and at remarkable yield (96%). Next, the established process model was used for the optimization of the overall process economics. Therefore, a comprehensive analysis of the process in terms of suitable reactor temperatures was performed based on a multi-objective function addressing important cost contributions in the integrated process (i.e. enzyme, desorbent, solid phase, substrate). The presented integrated process scheme can be easily adapted to a number of similar isomerization and epimerization reactions enabling economic production of (almost) the complete set of C6 sugars.


      PubDate: 2015-07-24T04:13:18Z
       
  • A catalytic hollow fibre membrane reactor for combined steam methane
           reforming and water gas shift reaction
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Ana Gouveia Gil, Zhentao Wu, David Chadwick, K. Li
      A catalytic hollow fibre membrane reactor (CHFMR) was developed in this study for combined steam methane reforming (SMR) and water gas shift (WGS) reaction. This is achieved by incorporating a Ni/SBA-15 catalyst into a plurality of micro-channels with open entrance from inner surface of Al2O3 hollow fibres, followed by coating of a 3.3µm Pd membrane on the outer surface of the hollow fibre using an electroless plating method. In addition to systematic characterizations of each reactor component, i.e. Ni/SBA-15 catalyst, micro-structured ceramic hollow fibre and Pd separating layer, the effect of how the reactor was assembled or fabricated on the catalytic performance was evaluated. Electroless plating of the Pd membrane impaired the catalytic performance of the deposited Ni/SBA-15 catalyst. Also, the over-removal of hydrogen from the reaction zone was considered as the main reason for the deactivation of the Ni-based catalyst. Instead of mitigating such deactivation using “compensating” hydrogen, starting the reaction at higher temperatures was found more efficient in improving the reactor performance, due to a better match between hydrogen production (from the reaction) and hydrogen removal (from the Pd membrane). An effective methane conversion of approximately 53%, a CO2 selectivity of 94% and a H2 recovery of 43% can be achieved at 560°C. In order for a more significant “shift” phenomenon, alternative methodology of fabricating the reactor and more coke resistant catalysts are recommended.


      PubDate: 2015-07-20T04:05:14Z
       
  • Linear general rate model of chromatography for core–shell
           particles: Analytical solutions and moment analysis
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Shamsul Qamar, Javeria Nawaz Abbasi, Aqsa Mehwish, Andreas Seidel-Morgenstern
      Due to their proven performance and improved availability, core–shell particles are increasingly applied for chromatographic separations. This paper presents semi-analytical solutions and a moment analysis of a detailed mathematical model for fixed-beds packed with core–shell particles. The model considers axial dispersion, interfacial mass transfer, intraparticle diffusion, linear adsorption, and the injection of rectangular pulses. The Laplace transformation is used as a basic tool to derive semi-analytical solutions. In addition the first three statistical temporal moments are derived from solutions in the Laplace domain. The numerical Laplace inversion is applied for back transformation of the solution in the actual time domain. In order to demonstrate their potential, different scenarios are considered to quantify the effects of the relative core size, axial dispersion, film mass transfer resistance and intraparticle diffusion resistance in the porous layer on the elution profiles. An important new result is the derivation of a plate height equation for fully porous and core–shell particles respecting the Danckwerts boundary conditions.


      PubDate: 2015-07-20T04:05:14Z
       
  • Breakup morphology of annular liquid sheet with an inner round air stream
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Hui Zhao, Jian-Liang Xu, Ju-Hui Wu, Wei-Feng Li, Hai-Feng Liu
      Experiments were performed on the deformation and breakup of annular liquid sheet of nine coaxial twin-fluid air-blast atomizers with water–air systems by using a high speed camera. Due to the morphological difference, the annular sheet breakup could be classified into three regimes, which were bubble (shell) breakup, Christmas tree (cellular) breakup and fiber breakup. The roles of atomizer size and Rayleigh–Taylor instability in the annular sheet breakup were studied. The correlations on the instability wavelength and the size of cellular structure were deduced. The results showed that the dimensionless cellular size was proportional to We −0.5, which were in good agreement with the experimental results. In order to have an overview of the different breakup mechanisms taking place over the wide range, we suggested categorizing these breakup regimes in a Weber number and dimensionless sheet thickness map.


      PubDate: 2015-07-20T04:05:14Z
       
  • Proton transfer mechanism of 1,3,5-tri(2-benzimidazolyl) benzene with a
           unique triple-stranded hydrogen bond network as studied by DFT-MD
           simulations
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Piyarat Nimmanpipug, Teerawit Laosombat, Vannajan Sanghiran Lee, Sornthep Vannarat, Suwabun Chirachanchai, Janchai Yana, Kohji Tashiro
      Clarification of proton transfer mechanisms is crucial to the development of proton exchange membrane fuel cells (PEMFCs). Nitrogen-containing heterocyclic compounds (e.g., imidazole derivatives) are well known for their potential to assist proton hopping through hydrogen bond networks at high temperatures. Among the many imidazole derivatives reported thus far, 1,3,5-tri(2-benzimidazolyl)benzene (TBIB) is assumed to be one of the most promising imidazole derivatives because of its triple-stranded three-dimensional hydrogen bond network. In fact, TBIB immersed into a polyphosphoric acid matrix was reported to enhance the proton conductivity to 10−2–10−1 S/cm in the high-temperature range up to 170°C. In the present work, the proton transfer mechanism has been investigated using density functional theory (DFT) with a DNP basis set and the GGA exchange-correlation functional BLYP and molecular dynamics simulations (MD) to provide insight into the cause of the remarkable proton conductivity of TBIB. Transition states in the proton hopping process were obtained using two types of models constructed from the X-ray crystal structure: an isolated two-molecule system (type I) and a periodic three-molecule system (type II). Alterations of charge distribution, molecular conformation and molecular orientation were investigated from these models. Further, the diffusion coefficient of proton transfer has been estimated and the mechanisms along three specific channels that favor efficient proton transfer between the layers have been examined in detail. Additionally, the effect of an electric field perturbation was investigated for these two models. The application of an external electric field was found to affect the proton hopping process remarkably, as evidenced by large changes in the activation energies and proton hopping times. In conclusion, the highly organized hydrogen-bonding network observed for TBIB was found to be a key factor in enhancing the efficiency of proton transfer.


      PubDate: 2015-07-20T04:05:14Z
       
  • Feature of acoustic sound signals involved in vapor bubble condensation
           and its application in identification of condensation regimes
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Jiguo Tang, Changqi Yan, Licheng Sun
      Experiments were carried out on the sound pressure oscillations condensation regime map, and bubble collapse frequency during the direct contact condensation of vapor with the aid of an acoustic hydrophone and a high-speed video camera. The injection rate of vapor and liquid subcooling in the experiments were 0.19–3.73m3/h and of 10–70K, respectively. Four different condensation regimes were identified according to features presented on the bubble surface and whether and when the bubble collapse occurred. The state-of-the-art signal processing methods (statistical, spectral, fractal and discrete wavelet transform analyses) were applied to processing the detected acoustic signals. The results showed that only the kurtosis and DWT in the four methods could distinguish the different regimes well. Furthermore, the spectral and fractal analyses showed that strongly persistent behavior in the signals corresponded to the dominant frequency in the range of 120–400Hz might be arisen from the periodic variation in the vapor bubble volume. While that corresponded to peaks with frequency higher than 7000Hz in transition and capillary wave regimes were probably the high-frequency oscillation in pressure induced by sudden bubble collapse. Contrarily, the first peak in 0–200Hz caused by the periodic bubble break-up or split-up was high anti-persistent. DWT analysis showed that the sound pressure oscillation introduced by bubble collapse was similar to that by bubble split-up for all condensation regimes, whereas at very high frequency two different types of oscillations arose. Furthermore, the bubble collapse frequency increased with increase in liquid subcooling and vapor injection rate, and could be obtained from the spectral and Hurst analyses of the signals indirectly.


      PubDate: 2015-07-20T04:05:14Z
       
  • Heat transfer and fluid flow analysis of a 4kW solar thermochemical
           reactor for ceria redox cycling
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Philipp Furler, Aldo Steinfeld
      A solar reactor consisting of a cavity-receiver containing a reticulated porous ceramic (RPC) foam made of CeO2 is considered for effecting the splitting of H2O and CO2 via a thermochemical redox cycle. A transient 3D heat and mass transfer model of the reduction step is formulated and solved using Monte-Carlo ray-tracing coupled to computational fluid dynamics. Experimental validation is accomplished in terms of measured temperatures and O2 evolution rates obtained with a solar reactor prototype tested under high-flux radiative power inputs in the range 2.8–3.8kW and mean solar concentration ratios up to 3024 suns. Critical temperatures of up to 2250K induced CeO2 sublimation, which in turn affected detrimentally the solar reactor performance. The model is applied to analyze an improved geometrical design with alternative flow configuration, enabling more uniform radiative absorption and temperature distributions, and resulting in a higher solar-to-fuel energy conversion efficiency.


      PubDate: 2015-07-20T04:05:14Z
       
  • Pressure drop in flow across ceramic foams—A numerical and
           experimental study
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): W. Regulski , J. Szumbarski , Ł. Łaniewski-Wołłk , K. Gumowski , J. Skibiński , M. Wichrowski , T. Wejrzanowski
      The unique properties of ceramic foams make them well suited to a range of applications in science and engineering such as heat transfer, reaction catalysis, flow stabilization, and filtration. Consequently, a detailed understanding of the transport properties (i.e. permeability, pressure drop) of these foams is essential. This paper presents the results of both numerical and experimental investigations of the morphology and pressure drop in 10ppi (pores per inch), 20ppi and 30ppi ceramic foam specimens with porosity in the range of 75–79%. The numerical simulations were carried out using a GPU implementation of the three-dimensional, multiple-relaxation-time lattice Boltzmann method (MRT-LBM) on geometries of up to 360 million nodes in size. The experiments were undertaken using a water channel. Foam morphology (porosity and specific surface area) was studied on post-processed, computed tomography (CT) images, and the sensitivity of these results to CT image thresholding was also investigated. Comparison of the numerical and experimental data for pressure drop exhibited very good agreement. Additionally, the results of this study were verified against other researchers׳ data and correlations, with varying outcomes.


      PubDate: 2015-07-16T01:57:48Z
       
  • A molecular dynamics study of water vapor nucleation in the presence of
           ions
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Chao Zhang , Yueshe Wang , Yingwen Liu , Yang Yang
      Ions make a significant contribution to the nucleation dynamics of aqueous aerosol particles, but the understanding about microscopic mechanism is insufficient. In this paper, molecular dynamics simulations are conducted to investigate the condensation of supersaturated water vapor in the presence and absence of ions. The Yasuoka–Matsumoto (YM) method and the kinetic analysis are extended to investigate the influence of ions on the nucleation dynamics. It is observed that the presence of ions has a dramatic influence on the water vapor nucleation, which makes the clustering of water molecules easily. The ion concentration and the supersaturation are key factors that control the phase transition in the simulation system. For a certain supersaturation, the generation rate of clusters is proportional to the ion density. Water molecules tend to condense around ions with negative charge and high electric quantity. In addition, details of the cluster change are explored by the kinetic analysis when the system is added with cations and anions simultaneously. It is found that the change rate of the cluster increases with the rise of ions and decreases with the rise of water molecules. This phenomenon can be related to the microscopic structure of clusters that water molecules wrap around the ions to form a shell. The coalescence effect plays an important role in the nucleation process, and the proportion of the coalescence effect increases as the increase of supersaturation.
      Graphical abstract image

      PubDate: 2015-07-16T01:57:48Z
       
  • Mass–count plots for crystal size control
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Daniel J. Griffin , Martha A. Grover , Yoshiaki Kawajiri , Ronald W. Rousseau
      We present measurements from batch crystallization as a trajectory in the phase space mapped out by the crystal mass and the total chord count. This new perspective yields a framework for monitoring and controlling crystallization that has two beneficial attributes: first, crystallization is seen as movement—we find that this fosters an intuitive understanding of crystallization kinetics; and, second, the problem of controlling the average crystal size is cast as a trajectory-endpoint control problem—we find that this promotes the development of spatially-oriented control schemes. The utility of the proposed framework is demonstrated by application. In particular, we apply the framework to: 1) elucidate the effects of simple temperature manipulations on the crystallization kinetics; 2) interpret the actions applied by supersaturation control (SSC) and direct nucleation control (DNC) to produce large crystals; and 3) develop a control scheme—termed spatially-guided action trajectory endpoint control (sGATEC)—that can be applied to produce crystals of pre-selected average size.
      Graphical abstract image

      PubDate: 2015-07-16T01:57:48Z
       
  • CaCO3 calcination by the simultaneous reduction of CuO in a Ca/Cu chemical
           looping process
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): J.M Alarcón , J.R. Fernández
      The exothermic reduction of CuO to Cu using a fuel gas as a source of heat to carry out the simultaneous calcination of CaCO3 in a fixed bed is evaluated. The absence of apparent large energy penalties, as in other chemical looping processes, is an indication that there is great potential for achieving a high level of energy efficiency with this Ca/Cu looping concept. A dynamic pseudo-homogeneous model has been developed to describe in detail the transient behavior of this operation in a fixed-bed reactor under adiabatic conditions. A sensitivity analysis of the main operating parameters (i.e. the CuO/CaCO3 molar ratio, starting temperature and fuel gas composition) confirms the theoretical viability of this operation. A balanced CuO/CaCO3 ratio ensures a suitable bed performance allowing the reduction and calcination fronts to advance together, reach moderate maximum temperatures of around 900°C and leave behind totally converted solids. The use of CO as fuel gas significantly reduces the CuO/CaCO3 ratio required for the CaCO3 calcination. A careful adjustment to bed composition must be carried out, since an excess of CuO in the bed will generate more heat than required for the calcination, and consequently hot spots higher than 1000°C will form along the bed. In contrast, an excess of CaCO3 will increase the energy demand and part of the bed will be left uncalcined.


      PubDate: 2015-07-12T01:51:27Z
       
  • Airlift bioreactor for biological applications with microbubble mediated
           transport processes
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Mahmood K.H. AL-Mashhadani , Stephen J. Wilkinson , William B. Zimmerman
      Airlift bioreactors can provide an attractive alternative to stirred tanks, particularly for bioprocesses with gaseous reactants or products. Frequently, however, they are susceptible to being limited by gas–liquid mass transfer and by poor mixing of the liquid phase, particularly when they are operating at high cell densities. In this work we use CFD modelling to show that microbubbles generated by fluidic oscillation can provide an effective, low energy means of achieving high interfacial area for mass transfer and improved liquid circulation for mixing. The results show that when the diameter of the microbubbles exceeded 200µm, the “downcomer” region, which is equivalent to about 60% of overall volume of the reactor, is free from gas bubbles. The results also demonstrate that the use of microbubbles not only increases surface area to volume ratio, but also increases mixing efficiency through increasing the liquid velocity circulation around the draft tube. In addition, the depth of downward penetration of the microbubbles into the downcomer increases with decreasing bubbles size due to a greater downward drag force compared to the buoyancy force. The simulated results indicate that the volume of dead zone increases as the height of diffuser location is increased. We therefore hypothesise that poor gas bubble distribution due to the improper location of the diffuser may have a markedly deleterious effect on the performance of the bioreactor used in this work.
      Graphical abstract image

      PubDate: 2015-07-12T01:51:27Z
       
  • Predicting and eliminating Joule heating constraints in large
           dielectrophoretic IDE separators
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Y. Wang , F. Du , M. Baune , J. Thöming
      Dielectrophoresis (DEP), a measure to manipulate motion trajectories of suspended particles, has a high potential for solving difficult particle–liquid separation problems. Applications of DEP so far have been limited to micro-channels and lab-on-a-chip devices. However, for designing DEP separators with sufficiently high throughput to reach preparative scale, an understanding of the interplay of channel geometry and electrode concept with respect to induced particle velocity is required. The objective of tailored design is a control of particle motion trajectories predominantly by DEP while avoiding electrothermal interference. It is Joule heating, which gives rise to temperature gradients in the liquid phase and, thus, induces thermal convection. In this work we demonstrate that a solution of this Joule heating problem in large scale DEP systems is a tailored ratio of electrode diameter, electrode distance, and channel height. Based on model calculations we predicted the influence of both DEP force and drag force through thermal convection on particle trajectories for a case study, a channel with rectangular cross section and an array of cylindrical interdigitated electrodes (IDE) at the bottom. These theoretical results were verified experimentally by measured velocities of polyelectrolytic resin microparticles located at the subsurface of demineralized water. This allowed for a qualitative sensitivity analysis of the impact of voltage input, particle size and medium properties on the critical design parameter. From this, design criteria were deduced for the IDE–DEP system that allow for minimizing the influence of Joule heating. The findings demonstrate that, even if high voltages are applied, Joule heating problems can be effectively suppressed in DEP system scale-up.


      PubDate: 2015-07-12T01:51:27Z
       
  • Production of formic acid from CO2 reduction by means of potassium
           borohydride at ambient conditions
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Cameron Fletcher , Yijiao Jiang , Rose Amal
      The present study provides an efficient process for the high-yield production of formic acid (24%) by reduction of carbon dioxide (CO2) with potassium borohydride at ambient conditions. The effects of reaction temperature, CO2 pressure and borohydride concentration have been investigated. For a 0.5M borohydride solution, 0.15mol/L of formic acid were produced at room temperature and ambient pressure with yields increasing at higher pressures. A time-resolved in situ 1H and 11B nuclear magnetic resonance (NMR) technique was firstly developed to monitor the elementary reaction processes under real working conditions. Direct evidence is given for the formation of H2, HD and a hydroxyborohydride intermediate (BH3OH−) formed during borohydride decomposition indicating that the source of the hydrogen gas comes from both the borohydride anion and water, while borohydride works as a water-splitting reagent. Consequently, a reaction mechanism involved in both borohydride hydrolysis and CO2 reduction has been established.


      PubDate: 2015-07-12T01:51:27Z
       
  • Transient effectiveness factors in the dynamic analysis of heterogeneous
           reactors with porous catalyst particles
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Claudia María Bidabehere , Juan Rafael García , Ulises Sedran
      A model to calculate the actual transient effectiveness factor in spherical porous catalyst particles in gradientless reactors, where a first order reaction takes place under isothermal conditions, linear equilibrium adsorption and intraparticle diffusion control, was developed. After a certain time has elapsed following a change in the feed׳s reactant concentration, the transient effectiveness factor can be approximated as a linear combination of the steady state effectiveness factor and the relative rate of change of the concentration in the fluid phase. Oppositely to the well-known steady state effectiveness factor, which depends only on the Thiele modulus ϕ , related to intrinsic properties of the catalysts, the transient effectiveness factor also depends on other two dimensionless numbers: α, the relationship between the capacity of accumulation of reactant in the fluid and solid phases, and ϕ f , a relationship between the convective flow and the intraparticle diffusion rate. In this way, the catalyst load, the reactor volume and the volumetric flow do impact on the effectiveness factor. The coefficients defined as I a and I f are the Diffusion–Adsorption–Reaction Factor and the Flow Factor, respectively, which are complex functions of the Thiele modulus, the convective modulus ϕ f and the system׳s adsorption capacity α, and which can be used to correct the steady state effectiveness factor to yield the approximated transient effectiveness factor, which is more exact. In the case of a pulse perturbation in the reactant׳s concentration, the transient effectiveness factor reaches a constant value which is larger than that from the steady state effectiveness factor and, the larger the catalyst mass and the flow, the larger the difference. Results show the existence of a pseudo-equilibrium state in gradientless reactors.


      PubDate: 2015-07-12T01:51:27Z
       
  • Study of gas hydrate metastability and its decay for hydrate samples
           containing unreacted supercooled liquid water below the ice melting point
           using pulse NMR
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Marat Sh. Madygulov , Anatoliy N. Nesterov , Alexey M. Reshetnikov , Valeriy A. Vlasov , Alexey G. Zavodovsky
      The behavior of bulk Freon-12 hydrate samples containing inclusions of unreacted liquid water below the ice melting point at pressures below the hydrate–ice–gas equilibrium pressure has been studied using nuclear magnetic resonance (NMR) spectroscopy. The amount of liquid water in the samples was directly measured by transverse relaxation measurements of the hydrogen nucleus of the system studied. An evidence of the long-lived existence of gas hydrate as a metastable phase and hydrate dissociation into supercooled water and gas has been presented. It was shown that the dissociation of the bulk metastable hydrate into supercooled water and gas was reversible. An influence of the phase state of the unreacted water in the samples on the stability of the metastable hydrate and mechanism of hydrate dissociation was revealed: ice crystallization led to the decay of the hydrate metastability and the hydrate dissociation into ice and gas.
      Graphical abstract image

      PubDate: 2015-07-12T01:51:27Z
       
  • Modelling of coffee extraction during brewing using multiscale methods: An
           experimentally validated model
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): K.M. Moroney , W.T. Lee , S.B.G. O׳Brien , F. Suijver , J. Marra
      Accurate and repeatable extraction of solubles from roasted and ground coffee with hot water is vital to produce consistently high quality coffee in a variety of brewing techniques. Despite this, there is an absence in the literature of an experimentally validated model of the physics of coffee extraction. In this work, coffee extraction from a coffee bed is modelled using a double porosity model, including the dissolution and transport of coffee. Coffee extraction experiments by hot water at 90°C were conducted in two situations: in a well stirred dilute suspension of coffee grains, and in a packed coffee bed. Motivated by experiment, extraction of coffee from the coffee grains is modelled via two mechanisms: an initial rapid extraction from damaged cells on the grain surface, followed by a slower extraction from intact cells in the grain kernel. Using volume averaging techniques, a macroscopic model of coffee extraction is developed. This model is parameterised by experimentally measured coffee bed properties. It is shown that this model can quantitatively reproduce the experimentally measured extraction profiles. The reported model can be easily adapted to describe extraction of coffee in some standard coffee brewing methods and may be useful to inform the design of future drip filter machines.
      Graphical abstract image Highlights

      PubDate: 2015-07-12T01:51:27Z
       
  • Iron-chloride ionic liquid immobilized on SBA-15 for solvent-free
           oxidation of benzyl alcohol to benzaldehyde with H2O2
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Ruibai Cang , Bin Lu , Xiaopeng Li , Rui Niu , Jingxiang Zhao , Qinghai Cai
      Iron-chloride immobilized ionic liquid (SIL-FeCl3) was prepared by N-methylimidazole reacting with chloropropylsilane linked on the mesoporous silica SBA-15 and coordinating of FeCl3 to the imidazolium chloride grafted on the surface, as proved by XRD, TEM, NMR, FT-IR, ICP–MS, UV–vis and N2 adsorption–desorption technique. The results showed that the supported FeCl3 species were mainly distributed on the surface with the nonuniform distribution and the coordination linkage of imidazole ring to FeCl3 was stronger enough to keep its not leaching from the surface. The SIL-FeCl3 was demonstrated to be an efficient catalyst for a solvent-free oxidation of benzyl alcohol to benzaldehyde (BzH) using H2O2 as oxidant, exhibiting high TON (125.8mol/molFe). The novelty of the manuscript is based on the distribution of iron species on the surface detected by TEM and EDX and the higher catalytic activity of the catalyst for effective oxidation of alcohol under solvent-free condition The catalyst can be easily recovered and effectively reused without a significant loss in its activity and selectivity, which would lead to its potential application foreground for environmental friendly synthesis of chlorine-free BzH.
      Graphical abstract image

      PubDate: 2015-07-12T01:51:27Z
       
  • A comparative study of Rh and Ni coated microchannel reactor for steam
           methane reforming using CFD with detailed chemistry
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Chenxi Cao , Nian Zhang , Xin Chen , Yi Cheng
      Steam methane reforming (SMR) in microchannel reactors has great potential for low-cost, compact hydrogen production due to intensified heat and mass transfer features and an evident reduction of reaction time from seconds to milliseconds. In this work simulation studies of an integrated microchannel reactor were carried out by using a detailed CFD model with elementary reaction kinetics. The model predictions were quantitatively validated by experimental data. The numerical simulations showed the comparison of catalytic performances of Rh and Ni catalysts for SMR in two operating modes, namely, inner-heating and outer-heating. The results demonstrated that Ni catalyst can exhibit excellent performance comparable to Rh under certain conditions. In the outer-heating mode, Ni showed much higher activity for water gas shift (WGS), which led to a higher H2/CO molar ratio in the products but more CO2 emission. In the inner-heating mode, during an initial stage of methane oxidation, complete oxidation of methane (COM) mainly happened on Ni, whereas partial oxidation of methane (POM) mainly occurred on Rh. The second stage was characterized by SMR and WGS, which then exhibited similar features as the outer-heating mode. Reaction path analysis showed that the surface C concentration on Rh in the inner-heating mode was lower than that in the outer-heating mode all along. The surface C concentration on Ni was very small in the initial stage of the inner-heating process, but strongly increased after O2 was consumed. Inner-heating operation is therefore preferred for reducing coking probability.


      PubDate: 2015-07-12T01:51:27Z
       
  • Screening of desulfurization adsorbent in metal–organic frameworks:
           A classical density functional approach
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Yu Liu , Fangyuan Guo , Jun Hu , Shuangliang Zhao , Honglai Liu , Ying Hu
      High-throughput screening of desulfurization adsorbent has been implemented by introducing a classical density functional theory (CDFT). The screening is focused on the adsorption capacity of dibenzothiophene (DBT) in 458 types of metal–organic frameworks (MOFs). Comparing to the state of art desulfurization adsorbent, the best MOF for low concentration (BMLC) shows an uptake 27 times of HKUST-1 while the best MOF for high concentration (BMHC) shows an uptake twice of HKUST-1. Hierarchical porous structure has been found in BMLC and BMHC, respectively. According to the radial distribution function, a layered adsorption mechanism has been found in BMLC instead of BMHC; and the thermodynamic differences between BMLC and BMHC can be understood by this lamellar adsorption mechanism.
      Graphical abstract image

      PubDate: 2015-07-07T03:16:56Z
       
  • Ensemble local kernel learning for online prediction of distributed
           product outputs in chemical processes
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Yi Liu , Zhengjiang Zhang , Junghui Chen
      The crystal size distribution in crystallization processes, the molecular weight distribution in polymerization processes, the particle size distribution in powder industries, and the pulp fiber length distribution in paper industries are all distributed product outputs. Reliable online quality prediction of these chemical processes with distributed outputs is important but challenging. In this work, the kernel learning (KL) framework is introduced to model and online predict the distributed product outputs. First, the KL method is proposed to construct a global distributed shape. Then, without resorting to a KL-based global distributed model, a just-in-time KL (JKL) model is presented for better description of local distributed shapes with more accurate and quick prediction performance. Moreover, an ensemble JKL (EJKL) modeling approach is developed to obtain more reliable prediction performance of the distributed outputs. The proposed modeling methods are applied to online prediction of the molecular weight distribution in polymerization processes and of the crystal size distribution in crystallization processes. The prediction results show the proposed method is superior to the traditional counterparts.


      PubDate: 2015-07-07T03:16:56Z
       
  • Effect of heating rate on the accuracy of measuring equilibrium conditions
           for methane and argon hydrates
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Anton Pavlovich Semenov , Vladimir Igorevich Medvedev , Pavel Aleksandrovich Gushchin , Vladimir Stanislavovich Yakushev
      This work examined the effect of the heating rate (from 0.2K/h (5.56·10−5 K/s) to 10K/h (277.78·10−5 K/s)) on the accuracy of measuring the three-phase equilibrium conditions for gas–liquid water–hydrate systems. The H2O+CH4 (CS-I) system was studied over the temperature range of 274.2–285.2K and the pressure range of 3.0–9.0MPa. Additionally, the H2O+Ar (CS-II) system was studied over the temperature and pressure ranges of 273.7–280.2K and 9.5–18.5MPa, respectively. The hydrate formation/dissociation experiments were performed in a Sapphire Rocking Cell RCS6 under isochoric conditions. Gas hydrates were formed using a 0.1% (w/w) solution of sodium dodecyl sulfate. It was found that the dissociation of the methane and argon hydrates (CS-I and CS-II, respectively) proceeds under conditions close to equilibrium at heating rates up to 0.5K/h (13.89·10−5 K/s). Significant deviations of the P,T-curve from the equilibrium line are observed at higher heating rates for methane hydrate (>281.2K) and argon hydrate (>277.2K). Our data on the equilibrium conditions of argon hydrate complement previous published data over the temperature range of 273.7–280.2K and the pressure range of 9.5–18.5MPa.
      Graphical abstract image

      PubDate: 2015-07-07T03:16:56Z
       
  • From the design to the development of a continuous fixed bed photoreactor
           for photocatalytic degradation of organic pollutants in wastewater
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): V. Vaiano , O. Sacco , D. Pisano , D. Sannino , P. Ciambelli
      For industrial applications of photocatalytic processes aimed to the removal of pollutants from wastewater, a good solution for a final scale-up would be the choice of a continuous catalytic fixed bed photoreactor, able to work both with artificial light and with solar light. The optimal design needs a deep study starting from fluid dynamic considerations, together with the evaluation of the light׳s distribution inside the reactor core. In this work, flat plate geometry was chosen and a structured bed photoreactor for wastewater treatment was designed and implemented starting from an optimized N-doped TiO2 photocatalyst immobilized on glass spheres. The fluid dynamic study of the structured bed reactor was intensely carried out through a CFD model. Instead of the traditional LVRPA, the Helmholtz equation, set with the Dirichlet conditions on the boundary, was used to model the light distribution inside the photoreactor. Based on the results of the modeling optimization, a laboratory scale photoreactor was developed. In order to obtain kinetic parameters, photocatalytic tests were carried out using a model pollutant. The Langmuir–Hinshelwood kinetic model was applied for estimating the kinetic parameters of the catalyst, starting from experimental data collected at different inlet pollutant concentrations. The kinetic expression together with the photons׳ spatial distribution was incorporated in the mass balance to achieve the theoretical distribution of the pollutant concentration in the reactor. The model was validated comparing the experimental data obtained at different contact times. The developed mathematical modeling allows to determine the best operating conditions to optimize the irradiation and the reactor volume, being a flexible method for a further scale-up of the photoreactor. The developed flat plate structured bed photoreactor was able to operate in continuous mode.


      PubDate: 2015-07-07T03:16:56Z
       
  • Shear dispersion in combined pressure-driven and electro-osmotic flows in
           a channel with porous walls
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Morteza Dejam , Hassan Hassanzadeh , Zhangxin Chen
      We present an analytical expression for the shear dispersion during transport of a neutral non-reacting chemical species within a channel with porous walls, which has not been addressed in previous studies, under the combined effects of pressure-driven and electro-osmotic flows. The continuity of concentrations and mass fluxes at the interface between the channel and the porous medium is applied to obtain the dispersion coefficient by considering a sufficiently low wall or zeta potential. The obtained dispersion coefficient is a function of the Debye–Hückel parameter, Poiseuille contribution fraction, and Péclet number. Results reveal that it is essential to include the exchange of chemical species between the electrolyte inside the channel and the porous medium. The results of this study find applications in design of solute transport through porous microfluidic networks and separation of emulsions in microchannel-membrane systems.


      PubDate: 2015-07-07T03:16:56Z
       
  • Rigorous modeling of CO2 absorption and chemisorption: The influence of
           bubble coalescence and breakage
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Michael C. Gruber , Stefan Radl , Johannes G. Khinast
      In this study, the impact of bubble breakage and coalescence (B&C) on the mass transfer and on the temporal evolution of species concentration during absorption and chemisorption is investigated. For this purpose, the CO2 absorption in water and the CO2 chemisorption in NaOH solutions of various initial pH serve as model cases. A three-dimensional Euler–Lagrange algorithm is used for the handling of the gaseous and the liquid phase in a model (simulation) of a laboratory-scale bubble column. The algorithm accurately forecasts the mean and fluctuating liquid velocities and predicts the bubble size distribution reasonably well. The results show that B&C critically impact mass transfer, liquid phase mixing, as well as reaction rates in systems with low to moderately large pH. In contrast, for extremely high pH values, shrinkage of bubbles becomes the dominating phenomenon. This is because bubble shrinkage leads to small bubbles, low gas hold-up, as well as little liquid phase agitation in the upper part of the reactor. Consequently, the relevance of B&C events decreases gradually with increasing pH. A plot of the results as function of the overall pH illustrates that a regime change occurs close to pH 12.5. This transition is caused by a dramatic reduction of the gas hold-up, leading to a significant reduction of liquid-phase agitation.
      Graphical abstract image

      PubDate: 2015-07-07T03:16:56Z
       
  • The method for steady states determination in tubular biofilm reactors
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Szymon Skoneczny , Bolesław Tabiś
      A method for determining the steady states in tubular reactors with biofilm on their inner walls is presented. The proposed method is general and can be used for modeling and design of aerobic processes in vertical and horizontal co-current tubular bioreactors. The proposed model can be extended for multi-substrate processes, aerobic as well as anaerobic. It was shown that bioreactor diameter strongly influences the degree of conversion of substrates. A new phenomenon was discovered, namely switching of profiles of concentrations of reagents in the biofilm. Interpretation of this phenomenon was given. It has been shown that by appropriate selection of the bioreactor diameter, it is possible to achieve high degrees of conversions of substrates at much lower residence times than in the continuous tank bioreactors.


      PubDate: 2015-07-07T03:16:56Z
       
  • Effect of solvent addition on bitumen–air bubble attachment in
           process water
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Lin He , Feng Lin , Xingang Li , Zhenghe Xu , Hong Sui
      Bitumen–air bubble attachment is an essential element for bitumen recovery from oil sands by flotation. Effect of solvent addition to bitumen on bitumen–air bubble attachment in an industrial process water was investigated by determining the minimum time required to achieve the bitumen–air bubble attachment, known as induction time. Proper addition of solvent to bitumen significantly reduced the induction time of bitumen–air bubble attachment, more so for naphtha than for toluene and reaching optimal at 10wt% solvent added to bitumen. The measurement of bubble coalescence time and total organic carbon content in the resulting process water revealed a critical role in bitumen–air bubble attachment of air bubble interfacial properties controlled primarily by surfactants in the process water and water chemistry. Increasing the solvent addition to bitumen led to an increased migration of natural surfactants to the bitumen–water interface. At a given solvent dosage, more surfactants adsorbed at toluene–diluted bitumen–water interface than at naphtha–diluted bitumen–water interface. Interestingly, zeta potentials of diluted bitumen droplets in the process water exhibited a maximum at about 10wt% of solvent addition to bitumen for both toluene and naphtha. At an identical dosage of solvent, toluene–diluted bitumen in the tailings water possesses a more negative zeta potential than naphtha–diluted bitumen. Finally, a possible adsorption mechanism of ions and surfactants accumulating at the diluted bitumen–water interface under the impact of solvent addition is proposed.
      Graphical abstract image

      PubDate: 2015-07-02T12:47:15Z
       
  • Modeling and simulation of soot combustion dynamics in a catalytic diesel
           particulate filter
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Valeria Di Sarli , Almerinda Di Benedetto
      In the work presented in this paper, a two-dimensional mathematical model of soot regeneration was developed for a single-channel catalytic diesel particulate filter. The commercial computational fluid dynamics (CFD) code ANSYS Fluent 15.0 was used to simulate the gas flow field, whereas the regeneration kinetics was implemented through user-defined-subroutines. Both mechanisms of catalyzed and non-catalyzed (i.e., thermal) oxidation were used to describe combustion of the soot trapped inside the porous wall of the filter. Conversely, only non-catalyzed oxidation was assumed for the cake layer. The aim of the work was at investigating the effect of the catalyst activity on the regeneration dynamics of the filter in the light of the thermal interaction between combustion of the soot in the (catalytic) porous wall and combustion of the cake. To this end, computations were run by increasing the pre-exponential factor in the Arrhenius equation for the catalytic reaction rate, thus simulating the effect of increasing catalyst activity. Numerical results have shown that, as the catalyst activity is increased, a transition occurs from a regime of slow combustion, in which regeneration proceeds in a substantially uniform manner over the filter, to a regime of intense combustion, in which regeneration proceeds by a reaction front moving upstream and downstream. The regime of slow combustion is characterized by low temperature rise (difference between the maximum filter temperature, T max , and the inlet gas temperature, T in , lower than 100K) and long time for cake consumption and, thus, filter regeneration (~1800s). It is established when the catalyst activity is too low to appreciably affect combustion of the cake. Thus, combustion of the cake occurs independently of what happens in the porous wall of the filter. In contrast, the regime of intense combustion is characterized by high temperature rise – (T max −T in )~400K – and short time for regeneration (~100s). It is established when the catalyst activity is high enough to make the porous wall of the filter an effective pilot for the cake. For this regime, the highest temperature rise is found under conditions that maximize the synchronization between combustion of the soot in the porous wall of the filter and combustion of the cake. When such a synchronization is attained, the time for filter regeneration becomes substantially insensitive to variations in the catalyst activity.
      Graphical abstract image

      PubDate: 2015-07-02T12:47:15Z
       
  • A further catalysis mechanism study on Amberlyst 35 resins application in
           alkylation desulfurization of gasoline
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Rong Wang , Jinbao Wan , Yonghong Li , Hongwei Sun
      Olefinic alkylation of thiophenic sulfurs (OATS) technology can be handled under mild conditions without any hydrogen consumption, which is a promising way to produce clean gasoline. However, the side reaction in this desulfurization process would lead to significant levels of coke. To maintain the high activity for alkylation of sulfurs, the selectivity of OATS catalyst must be improved by reducing side reactions. In this paper, the catalytic mechanism of macroporous sulfonic resins Amberlyst 35 (A35) in the OATS process was further investigated by the calculation of density functional theory (DFT), to understand the reaction path of different reactant at molecular level. The calculated results indicated that the beginning of main and side reactions were both from a stable alkoxide intermediate, which was the protonation product of adsorbed olefin on the catalyst. Compared with alkenes, thiophenic compounds were more inclined to be coadsorbed on the alkoxide intermediate for further reaction, and the alkylation rate of sulfurs with alkenes was faster than the self-dimerization of alkenes. Moreover, the calculated results also indicated that the alkylation of thiophenic sulfurs as main reaction was exothermic while the dimerization of alkenes as side reaction was endothermic over A35. Additionally, the conversion curves of different reactants over A35 and the related kinetics at different temperature were also studied by experimental methods. The obtained experimental results could be used to verify the reliability of relevant theoretical calculations. Based on the differences in the reaction mechanisms obtained by the theoretical and experimental studies, two measures were proposed, which would be useful to reduce side reactions to a lower extent. The study would be beneficial to the further industrial application of A35 in the alkylation desulfurization of gasoline.
      Graphical abstract image

      PubDate: 2015-07-02T12:47:15Z
       
  • Nonlinear frequency response analysis of forced periodic operation of
           non-isothermal CSTR with simultaneous modulation of inlet concentration
           and inlet temperature
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Daliborka Nikolić , Andreas Seidel-Morgenstern , Menka Petkovska
      The nonlinear frequency response (NFR) method is applied for evaluation of possible improvement through simultaneous periodic modulation of two inputs of a non-isothermal continuously stirred tank reactor (CSTR) in which homogeneous nth order reaction A→product(s) takes place. The two modulated inputs are the concentration of the reactant in the feed steam and the temperature of the feed stream. The cross asymmetrical second order FRF which correlates the outlet concentration with both modulated inputs is derived and analyzed. The optimal phase difference which should be used in order to maximize the conversion is determined. The method is tested on three numerical examples of non-isothermal CSTRs: (a) one which is oscillatory stable with strong resonant behavior, (b) one which is oscillatory stable with weak resonant behavior and (c) one which is nonoscillatory stable. Good agreement between the results of the approximate NFR method and the results of “exact” numerical integration is obtained except for the reactor with strong resonance for forcing frequencies which are close to the resonant frequency and for the reactor with weak resonant behavior for forcing frequency equal to the resonant one in case of high forcing amplitudes.


      PubDate: 2015-07-02T12:47:15Z
       
  • Development of a coalescence model due to turbulence for the population
           balance equation
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): S.K. Das
      The current research introduces a new mathematical framework to develop coalescence models for turbulent flows in the context of population balance equations. Previous researchers have modeled the coalescence term as two independent factors: the collision rate and the coalescence efficiency. In contrast, the new approach formulates the coalescence term as a single entity and directly accounts for the effect of turbulence on the probability of coalescence. It also considers the angle between the line of centers and the relative velocity of the bubbles. The coalescence model becomes complete when the interaction and the drainage times are incorporated in the new framework. The model is then tested successfully against experimental data from the literature. A few parametric runs to study the behavior of the coalescence kernel complete the paper.


      PubDate: 2015-07-02T12:47:15Z
       
  • On-line measurement of the real size and shape of crystals in stirred tank
           crystalliser using non-invasive stereo vision imaging
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Rui Zhang , Cai Y. Ma , Jing J. Liu , Xue Z. Wang
      Non-invasive stereo vision imaging technique was applied to monitoring a cooling crystallisation process in a stirred tank for real-time characterisation of the size and shape of needle-like l-glutamic acid (L-GA) β polymorphic crystals grown from solution. The instrument consists of two cameras arranged in an optimum angle that take 2D images simultaneously and are synchronised with the lighting system. Each 2D image pair is processed and analysed and then used to reconstruct the 3D shape of the crystal. The needle shaped L-GA β form crystal length thus obtained is found to be in good agreement with the result obtained from off-line analysis of crystal samples, and is about three times larger than that estimated using 2D imaging technique. The result demonstrates the advantage of 3D imaging over 2D in measurement of crystal real size and shape.


      PubDate: 2015-07-02T12:47:15Z
       
  • A nonlinear Cole–Cole model for large-amplitude electrochemical
           impedance spectroscopy
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): C. Hernandez-Jaimes , J. Vazquez-Arenas , J. Vernon-Carter , J. Alvarez-Ramirez
      Electrochemical impedance spectroscopy (EIS) is increasingly used to monitor the behavior of electrochemical processes. Commonly, EIS is driven by an input signal comprised of a small-amplitude sinusoidal wave superimposed on a constant dc potential (i.e., potentiostatic) to facilitate its analysis through a linearization methods. However, valuable information of electrochemical processes can be also collected at large-amplitude perturbation voltages, which can excite nonlinearities reflected as amplitude-dependent impedances. The aim of this work is to explore a tractable formalism to derive nonlinear transfer functions to describe the EIS response under large amplitude perturbation signals. Gelatinized starch suspension is used as simple case study to determine the parameters of the nonlinear elements. A nonlinear extension of the Cole–Cole equation is proposed to account for the EIS measurements recorded at different amplitudes, where its frequency response is computed by means of first-harmonic balance and Fourier approximation of nonlinearities. The nonlinear Cole–Cole model is comprised of nonlinear resistances and constant phase elements. Unlike linear behavior, the nonlinear response of EIS cannot be obtained explicitly, but through numerical analysis of a set of nonlinear equations. The resulting transfer function leads to a nonlinear fractional equation, where the frequency response depends on the signal amplitude under voltage excitation.


      PubDate: 2015-07-02T12:47:15Z
       
  • New insights into fabrication of hydrophobic/hydrophilic composite hollow
           fibers for direct contact membrane distillation
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Jiaming Zhu , Lanying Jiang , Takeshi Matsuura
      Dual-layer composite membrane is a new design for direct contact membrane distillation (DCMD) with membrane performance potentially superior to that of single layer porous membranes. Using dry–wet phase inversion technology, novel dual-layer hollow fiber membranes were fabricated in current research. The outer layer was made from polyvinylidene fluoride (PVDF) with polyvinylpyrolidone (PVP) or glycerol as non-solvent additive, while the inner layer consists of PVDF and polyvinyl alcohol (PVA) blend. The effect of the nonsolvent additive type in the outer layer and that of PVA/PVDF blending ratio in the inner layer on the morphological, mechanical and separation characteristics of the composite membranes was investigated. Membrane performance was further correlated to the physicochemical and morphological characteristics of the membranes. In particular, a thorough investigation of pore wetting in DCMD was attempted for the first time in this work, observing the cross-sectional distribution of EDX chlorine signals as an indication of the penetration of sodium chloride solution into the pore from the feed.


      PubDate: 2015-07-02T12:47:15Z
       
  • Formation of polycyclic aromatic hydrocarbons in Claus process from
           contaminants in H2S feed gas
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Shabin Mohammed , Abhijeet Raj , Ahmed Al Shoaibi , P Sivashanmugam
      Claus process is used in oil and gas industry to produce sulfur from H2S. The presence of aromatic contaminants in its feed is believed to have detrimental effect on the process, as they are able to survive the high-temperature environment of Claus furnace and reach the catalytic units, where they form soot, clog catalyst pores, and deactivate them. Along with aromatics, small hydrocarbons (CH4, C2H6, and C3H8) are also present in feed that are capable of forming polycyclic aromatic hydrocarbons (PAHs) and soot in anoxic, high-temperature environment of the furnace. In this work, a detailed reaction mechanism with 258 species and 1695 reactions for Claus feed containing H2S, aliphatic and aromatic hydrocarbons, CO, CO2 and H2O is developed. The mechanism includes reactions for PAH formation (up to coronene) from hydrocarbons, H2S oxidation, and the interaction of hydrocarbons with S-containing species. The mechanism is validated using experimental species and aromatics profiles in flames. Through furnace simulations, the fate of aromatic contaminants, the amount of PAHs formed from hydrocarbon contaminants and the temperature effects on PAH profiles are determined. The PAH formation pathways are found, and the role of resonantly stabilized radicals is highlighted.


      PubDate: 2015-07-02T12:47:15Z
       
  • Operating optimality assessment and nonoptimal cause identification for
           non-Gaussian multimode processes with transitions
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Yan Liu , Fuli Wang , Yuqing Chang , Ruicheng Ma
      Generally, process operating performance affects the economic benefits of enterprises, which prompts the development of process operating performance assessment. In this study, a novel operating optimality assessment and nonoptimal cause identification strategy is proposed for non-Gaussian multimode processes. Compared with the reported methods, the advantages of the proposed method are: (i) non-Gaussian distribution data is firstly considered in operating optimality assessment; (ii) besides the online assessment strategy for stable mode, that for transitional mode is developed for the first time; (iii) a novel online mode identification method is developed based on the sample posterior probabilities together with a predefined threshold, which can not only improve the accuracy of the assessment results but also reduce the risk of misclassification; (iv) the nonoptimal cause identification approach is established to identify the variables responsible for the nonoptimal performance. Finally, the effectiveness of the proposed method is demonstrated by Tennessee Eastman (TE) process.


      PubDate: 2015-07-02T12:47:15Z
       
  • Preparation of biodegradable polymeric nanoparticles for pharmaceutical
           applications using glass capillary microfluidics
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Rahimah Othman , Goran T. Vladisavljević , Zoltan K. Nagy
      The aim of this study was to develop a new microfluidic approach for the preparation of nanoparticles with tuneable sizes based on micromixing/direct nanoprecipitation in a coaxial assembly of tapered-end glass capillaries. The organic phase was 1wt% poly(ε-caprolactone) (PCL) or poly(dl-lactic acid) (PLA) in tetrahydrofuran and the antisolvent was Milli-Q water. The size of nanoparticles was precisely controlled over a range of 190–650nm by controlling phase flow rates, orifice size and flow configuration (two-phase co-flow or counter-current flow focusing). Smaller particles were produced in a flow focusing device, because the organic phase stream was significantly narrower than the orifice and remained narrow for a longer distance downstream of the orifice. The mean size of PCL particles produced in a flow focusing device with an orifice size of 200μm, an organic phase flow rate of 1.7mLh−1 and an aqueous-to-organic flow rate ratio of 10 was below 200nm. The size of nanoparticles decreased with decreasing the orifice size and increasing the aqueous-to-organic phase flow rate ratio. Due to higher affinity for water and amorphous structure, PLA nanoparticles were smaller and exhibited a smoother surface and more rounded shape than PCL particles.
      Graphical abstract image

      PubDate: 2015-07-02T12:47:15Z
       
  • PSF hollow fiber membrane fabricated from
           PSF–HBPE–PEG400–DMAc dope solutions via reverse
           thermally induced phase separation (RTIPS) process
    • Abstract: Publication date: 1 December 2015
      Source:Chemical Engineering Science, Volume 137
      Author(s): Long-Bao Zhao , Min Liu , Zhen-Liang Xu , Yong-Ming Wei , Min-Xian Xu
      Hyperbranched polyesters (HBPEs) based on 2,2-bis(methylol)propionic acid (bis-MPA) was used as an additive to prepare polysulfone (PSf) hollow fiber membranes while the PSf–HBPE–PEG400–DMAc dope solutions were low critical solution temperature (LCST) membrane-forming systems. When the temperature of the coagulation bath was lower than the cloud point, the membrane formation process was the NIPS process, and the finger-like structure could be found in the membranes. The hydrophilicity, porosity, pure water flux, mean effective pore size and breaking strength of these prepared membranes increased with increasing the HBPE content. On the other hand, when the temperature of the coagulation bath reached the cloud point, the membrane formation process was changed to the reverse thermally induced phase separation (RTIPS) process. In these membranes, the finger-like structure was replaced by the sponge-like structure, and the porosity, pure water flux, mean effective pore size and breaking strength of these prepared membranes increased with increasing the temperature of the coagulation bath.


      PubDate: 2015-07-02T12:47:15Z
       
 
 
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